From the analysis of extensive nucleotide sequence data available for the env and gag genes of HIV-1, it has become clear that six subtypes of the virus can be identified. However, the immunologic relatedness of these various HIV-1 subtypes has not yet been examined. We propose to determine if serotypes of the virus exist, and if these serotypes parallel or diverge from the aforementioned sequence-based subtypes. Moreover, we will investigate whether intra-typic groups can be identified immunologically. To do this, we plan, first, to use several of the 60 anti-HIV human monoclonal antibodies (mAbs) which have been produced in our laboratory. These mAbs were induced by viral proteins during the course of natural human infection with HIV-1, Type B (the subtype which predominates in the United States). These mAbs were selected on the basis of their reactivity with Type B-HIV-1; they are specific for various regions of gp120, gp41, p24 and p17. Particular emphasis will be placed on studies of mAbs specific for the V3 loop and the CD4 binding domain of gp120, two epitopes in the extracellular domain of gp41, and various regions of p24. All of these mAbs will be tested for their ability to bind to viral lysates prepared from primary isolates of each of the six HIV-1 subtypes. Relevant anti-gp 120 nd gp41 mAbs will be tested as well for their ability to bind to the surface of infected cells and to neutralize and lyse viral specimens. In addition to determining whether these reagents can illuminate serotypes and intra-typic viral classes, we will determine if these mAbs can distinguish between various phenotypic groups of HIV-1 such as macrophage-tropic and T-cell tropic strains. Next, we propose to produce new human mAbs that will be selected on the other (non-Type B) HIV- 1 subtypes. These new mAbs will be characterized with respect to (a) their immunochemical reactivity, i.e., their epitopes, conformation-dependence, Kd, koo, etc.. (b) their biologic function, i.e., neutralizing and virolytic activity, and (c) their ability to distinguish and/or cross-react with diverse viral serotypes. The data generated using these various mAbs and viral subtypes will be analyzed by cluster analysis and other defined statistical techniques. This analysis will generate an immunologic classification scheme which will permit the various primary isolates from around the world to be divided into serotypes and intra-typic groups. This immunologic classification will be compared to tahe genotypic classification. Those mAbs which we identify as most useful for distinguishing serotypes and intra-typic groups will be selected for use in a serotyping panel which will be made available tot he scientific community for large-scale studies of global primary isolates. The immunologic classification scheme and the reagents that will be generated will be critical to the design of global strategies for the development of HIV vaccines and the selection of reagents for use in passive immunization to prevent the transmission of HIV-1.